My espresso machine has a pretty impressive drip tray, at just around 1.5 liters in capacity, it holds quite a bit.
The problem is, if I empty it only when full, the bottom part of it has this really slippery, rather slimy surface which is extremely difficult to scrub. To be clear, it comes off easy enough, but tends to collect in nooks and corners.
I've tried adding a cap full of vinegar to the tray after cleaning and replacing it, this didn't make a noticeable difference. Even if I empty the tray when it's half full, there's still a bit of build up.
Is there anything else I can put in the bottom of the tray that wouldn't come with any competing odors to the coffee I'm brewing, but help keep this (as far as I can tell) 'water gunk' from forming? I'd really like to avoid dumping and cleaning the tray daily, as it is a bit of a chore.